Jordan Peterson's argument (tl;dr): "The disgust mechanism is an evolutionary response to disease, and therefore in the modern world irrelevant" (his idea in my words. I do not feel like transcribing his verbiage at the moment.)
Perhaps it is true that the disgust mechanism is a defense mechanism against spreading disease among populations, and perhaps in pre-vaccination times this was extremely useful, but perhaps not so useful today. Peterson fails to recognize that the defense mechanism which kept mankind divided within their own relatively insular tribes, kingdoms, and nations, also gave way to biological differentiation over time, which, as we are taught by the current Human Biological Diversity and race realist circles, can produce disastrous consequences when placed in the same petri dish- with some populations genetically predisposed to produce competitive and contradictory ways of life that result in social strife, conflict, and deflation of trust as we see in the modern West today being colonized by the Third World.
Imagine if all Europeans lacked the disgust mechanism of the nationalists and all voted Labor. In no time Europe would become a giant rape party for the lowest, savage, and intellectually pitiful Muslim Africans and Arabs. Europe would be destroyed. In fact it already is. That disgust mechanism at least gives Europe a fighting shot.
In this case the disgust mechanism is a self-perpetuating fact of life. Disease -> Disgust -> isolation -> biological differentiation -> behavioral divergence -> divergent social organization -> disgust -> (repeat)